Method and apparatus for controlling the operation of a terminal device

ABSTRACT

According to one aspect there is provided a method in an apparatus in a first network operating according to a first radio access technology, RAT, the method comprising evaluating ( 101 ) parameters and/or rules for a terminal device as part of an access network selection, traffic steering and/or traffic aggregation procedure between the first network and a second network operating according to a second RAT; starting ( 103 ) a timer if the parameters and/or rules are satisfied; and adjusting ( 105 ) the operation of the timer in the event that a change or potential change to the parameters and/or rules occurs prior to expiry of the timer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/327,943, filed Jan. 20, 2017, which is a U.S. National Phase entryunder 35 U.S.C. § 371 from PCT International Application No.PCT/SE2015/050643, filed Jun. 3, 2015, which claims benefit of priorityto Provisional Application No. 62/038,655, filed Aug. 18, 2014, all ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to terminal devices thatsupport multiple radio access technologies, RATs, and more particularlyrelates to controlling the operation of terminal devices with respect toradio access networks, RANs, operating according to different RATs.

BACKGROUND

The wireless local-area network (WLAN) technology known as “Wi-Fi” hasbeen standardized by IEEE in the 802.11 series of specifications (i.e.,as “IEEE Standard for Information technology—Telecommunications andinformation exchange between systems. Local and metropolitan areanetworks—Specific requirements. Part 11: Wireless LAN Medium AccessControl (MAC) and Physical Layer (PHY) Specifications”). As currentlyspecified, Wi-Fi systems are primarily operated in the 2.4 GHz or 5 GHzbands.

Cellular operators that are currently serving mobile users with, forexample, any of the technologies standardized by the 3rd-GenerationPartnership Project (3GPP), including the radio-access technologiesknown as Long-Term Evolution (LTE), Universal Mobile TelecommunicationsSystem (UMTS)/Wideband Code-Division Multiple Access (WCDMA), High SpeedPacket Access (HSPA) and Global System for Mobile Communications (GSM),see Wi-Fi as a wireless technology that can provide good additionalsupport for users in their regular cellular networks. There is interestaround using the Wi-Fi technology as an extension, or alternative tocellular radio access network technologies to handle the alwaysincreasing wireless bandwidth demands. The term “operator-controlledWi-Fi” points to a Wi-Fi deployment that on some level is integratedwith a cellular network operator's existing network and where the 3GPPradio access networks and the Wi-Fi wireless access may even beconnected to the same core network and provide the same services.

However, most current Wi-Fi/WLAN deployments are totally separate frommobile cellular communication networks, and can be seen asnon-integrated from the terminal device's perspective. Most operatingsystems (OSs) for terminal devices such as Android™ and iOS®, support asimple Wi-Fi offloading mechanism where a user equipment, UE (the termused to refer to terminal devices by 3GPP) immediately switches all itsInternet Protocol (IP) traffic or Packet-Switched (PS) bearers to aWi-Fi network upon a detection of a suitable network with a receivedsignal strength above a certain level. Henceforth, the decision tooffload to a Wi-Fi or not is referred to as access network selectionand/or traffic steering and the term “Wi-Fi-if-coverage” is used torefer to the aforementioned strategy of selecting Wi-Fi whenever such anetwork is detected.

There are several drawbacks of the “Wi-Fi-if-coverage” strategy, whichhas led to intense activity in the area of operator-controlled Wi-Fi inseveral standardization organizations. In 3GPP, activities to connectWi-Fi access points to the 3GPP-specified core network are pursued, andin Wi-Fi alliance, WFA, activities related to certification of Wi-Fiproducts are undertaken, which to some extent also is driven from theneed to make Wi-Fi a viable wireless technology for cellular operatorsto support high bandwidth offerings in their networks. The term Wi-Fioffload is commonly used and points towards that cellular networkoperators seek means to offload traffic from their cellular networks toWi-Fi, e.g., in peak-traffic-hours and in situations when the cellularnetwork for one reason or another needs to be off-loaded, e.g., toprovide requested quality of service, maximize bandwidth or simply forcoverage.

Furthermore, 3GPP has agreed to specify a feature/mechanism forWLAN/3GPP Radio interworking which improves operator control withrespect to how a UE performs access selection and/or traffic steeringbetween 3GPP and WLANs belonging to the operator or its partners (it mayeven be so that the mechanism can be used for other, non-operator, WLANsas well, even though this is not the main target), and it is expectedthat the mechanism will be included in Release 12 of the 3GPPspecifications for LTE.

In the mechanism, parameters and/or rules are evaluated for one or bothof the 3GPP network and WLAN to determine if a terminal device that iscurrently using the 3GPP network should access and/or steer traffic tothe WLAN and vice versa. According to the mechanism the parametersand/or rules must be satisfied for a certain time period before theterminal device accesses and/or steers traffic to a different network.The certain time period is monitored using a timer which is started whenthe parameters and/or rules are first satisfied. This timer is alsoreferred to herein as a time-to-trigger tinier, since it indicates forhow long the parameters and/or rules have to be satisfied before thechange in access network or traffic steering is triggered. One reasonfor the use of the timer is to avoid a terminal device from‘ping-ponging’ between the 3GPP network and WLAN.

SUMMARY

Thus, when the parameters and/or rules are met for a terminal device toaccess or steer traffic to a network operating according to another RAT,the timer is activated and provided that the parameters and/or rules arestill met when the timer expires, the terminal device accesses or steerstraffic to the other network.

However, a problem exists with the use of the timer in that it ispossible for the parameters and/or rules to change or be updated whilethe timer is running. If the timer is allowed to continue running, itmay be that the terminal device executes the change in access network ortraffic steering earlier than configured by the network. For example, ifthe time to trigger is configured to be five seconds and the conditionsfor steering have been fulfilled for four seconds when the terminaldevice receives a new threshold and/or condition configuration from thenetwork, the terminal device would execute the change in access networkor steering one second after receiving the new configuration, eventhough the network would expect (and probably want) the terminal deviceto apply a full five second timer duration when evaluating the newparameters and/or rules. This use of the timer may result inping-ponging which impairs user experience due to interruptions,increases signalling overhead, and also leads to UE behaviour that isnot expected by the network.

Therefore, there is a need for an improved technique for controlling theoperation of a terminal device with respect to networks operatingaccording to different RATs.

According to a first aspect, there is provided a method in an apparatusin a first network operating according to a first radio accesstechnology, RAT, the method comprising evaluating parameters and/orrules for a terminal device as part of an access network selection,traffic steering and/or traffic aggregation procedure between the firstnetwork and a second network operating according to a second RAT;starting a timer if the parameters and/or rules are satisfied; andadjusting the operation of the timer in the event that a change orpotential change to the parameters and/or rules occurs prior to expiryof the timer.

According to a second aspect, there is provided a computer programproduct comprising a computer readable medium having computer readablecode embodied therein, the computer readable code being configured suchthat, on execution by a suitable computer or processor, the computer orprocessor is caused to perform the method described above.

According to a third aspect, there is provided an apparatus for use in afirst network operating according to a first radio access technology,RAT, the apparatus being adapted to evaluate parameters and/or rules fora terminal device as part of an access network selection, trafficsteering and/or traffic aggregation procedure between the first networkand a second network operating according to a second RAT; start a timerif the parameters and/or rules are satisfied; and adjust the operationof the timer in the event that a change or potential change to theparameters and/or rules occurs prior to expiry of the timer.

According to a fourth aspect, there is provided a method in a firstapparatus in a first network operating according to a first radio accesstechnology, RAT, the method comprising sending an indication to a secondapparatus in the first network, the indication indicating the way inwhich the operation of a timer is to be adjusted in the event that achange or potential change to parameters and/or rules occurs prior toexpiry of the timer, wherein the parameters and/or rules are evaluatedby the second apparatus for a terminal device as part of an accessnetwork selection, traffic steering and/or traffic aggregation procedurebetween the first network and a second network operating according to asecond RAT.

According to a fifth aspect, there is provided a computer programproduct comprising a computer readable medium having computer readablecode embodied therein, the computer readable code being configured suchthat, on execution by a suitable computer or processor, the computer orprocessor is caused to perform the method described above.

According to a sixth aspect, there is provided a first apparatus for usein a first network operating according to a first radio accesstechnology, RAT, the first apparatus being adapted to send an indicationto a second apparatus in the first network, the indication indicatingthe way in which the operation of a timer is to be adjusted in the eventthat a change or potential change to parameters and/or rules occursprior to expiry of the timer, wherein the parameters and/or rules areevaluated by the second apparatus for a terminal device as part of anaccess network selection, traffic steering and/or traffic aggregationprocedure between the first network and a second network operatingaccording to a second RAT.

According to a seventh aspect, there is provided an apparatus for use ina first network operating according to a first radio access technology,RAT, the apparatus comprising an evaluation module evaluating parametersand/or rules for a terminal device as part of an access networkselection, traffic steering and/or traffic aggregation procedure betweenthe first network and a second network operating according to a secondRAT; a starting module for starting a timer if the parameters and/orrules are satisfied; and an adjusting module for adjusting the operationof the timer in the event that a change or potential change to theparameters and/or rules occurs prior to expiry of the timer.

According to an eighth aspect, there is provided a first apparatus foruse in a first network operating according to a first radio accesstechnology, RAT, the first apparatus comprising a sending module forsending an indication to a second apparatus in the first network, theindication indicating the way in which the operation of a timer is to beadjusted in the event that a change or potential change to parametersand/or rules occurs prior to expiry of the timer, wherein the parametersand/or rules are evaluated by the second apparatus for a terminal deviceas part of an access network selection, traffic steering and/or trafficaggregation procedure between the first network and a second networkoperating according to a second RAT.

According to a ninth aspect, there is provided an apparatus for use in afirst network operating according to a first radio access technology,RAT, the apparatus comprising a processor and a memory, said memorycontaining instructions executable by said processor whereby saidapparatus is operative to: evaluate parameters and/or rules for aterminal device as part of an access network selection, traffic steeringand/or traffic aggregation procedure between the first network and asecond network operating according to a second RAT; start a timer if theparameters and/or rules are satisfied; and adjust the operation of thetimer in the event that a change or potential change to the parametersand/or rules occurs prior to expiry of the timer.

According to a tenth aspect, there is provided a first apparatus for usein a first network operating according to a first radio accesstechnology, RAT, the first apparatus comprising a processor and amemory, said memory containing instructions executable by said processorwhereby said apparatus is operative to: send an indication to a secondapparatus in the first network, the indication indicating the way inwhich the operation of a timer is to be adjusted in the event that achange or potential change to parameters and/or rules occurs prior toexpiry of the timer, wherein the parameters and/or rules are evaluatedby the second apparatus for a terminal device as part of an accessnetwork selection, traffic steering and/or traffic aggregation procedurebetween the first network and a second network operating according to asecond RAT.

Various specific and exemplary embodiments of the above aspects aredescribed in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the techniques introduced in this document aredescribed below with reference to the following figures, in which:

FIG. 1 is a non-limiting example block diagram of an LTE cellularcommunications network;

FIG. 2 is a block diagram of a terminal device according to anembodiment;

FIG. 3 is a block diagram of a radio access network node according to anembodiment;

FIG. 4 is a block diagram of a core network node according to anembodiment;

FIG. 5 is a block diagram of a WLAN access point according to anembodiment;

FIG. 6 is a diagram illustrating one example of a network interworkingfeature;

FIG. 7 illustrates a method of operating an apparatus according to anembodiment;

FIG. 8 illustrates a method of operating a network node according to anembodiment; and

FIG. 9 illustrates a method of operating an apparatus according to aspecific embodiment.

DETAILED DESCRIPTION

The following sets forth specific details, such as particularembodiments for purposes of explanation and not limitation. But it willbe appreciated by one skilled in the art that other embodiments may beemployed apart from these specific details. In some instances, detaileddescriptions of well known methods, nodes, interfaces, circuits, anddevices are omitted so as not obscure the description with unnecessarydetail. Those skilled in the art will appreciate that the functionsdescribed may be implemented in one or more nodes using hardwarecircuitry (e.g., analog and/or discrete logic gates interconnected toperform a specialized function, ASICs, PLAs, etc.) and/or using softwareprograms and data in conjunction with one or more digitalmicroprocessors or general purpose computers. Nodes that communicateusing the air interface also have suitable radio communicationscircuitry. Moreover, the technology can additionally be considered to beembodied entirely within any form of computer-readable memory, such assolid-state memory, magnetic disk, or optical disk containing anappropriate set of computer instructions that would cause a processorand also in some cases a receiver component and/or transmitter componentto carry out the techniques described herein.

Hardware implementation may include or encompass, without limitation,digital signal processor (DSP) hardware, a reduced instruction setprocessor, hardware (e.g., digital or analog) circuitry including butnot limited to application specific integrated circuit(s) (ASIC) and/orfield programmable gate array(s) (FPGA(s)), and (where appropriate)state machines capable of performing such functions.

In terms of computer implementation, a computer is generally understoodto comprise one or more processors, one or more processing units, one ormore processing modules or one or more controllers, and the termscomputer, processor, processing unit, processing module and controllermay be employed interchangeably. When provided by a computer, processor,processing unit, processing module or controller, the functions may beprovided by a single dedicated computer, processor, processing unit,processing module or controller, by a single shared computer, processor,processing unit, processing module or controller, or by a plurality ofindividual computers, processors, processing units, processing modulesor controllers, some of which may be shared or distributed. Moreover,the terms “processor”, “processing unit”, “processing module” or“controller” also refer to other hardware capable of performing suchfunctions and/or executing software, such as the example hardwarerecited above.

Although the description is given for a terminal device or userequipment (UE), it should be understood by the skilled in the art that“terminal device” and “UE” are non-limiting terms comprising any mobile,non-mobile or wireless device or node equipped with a radio interfaceallowing for at least one of: transmitting signals in uplink (UL) andreceiving and/or measuring signals in downlink (DL). A UE herein maycomprise a UE (in its general sense) capable of operating or at leastperforming measurements in one or more frequencies, carrier frequencies,component carriers or frequency bands. It may be a “UE” operating insingle- or multi-radio access technology (RAT) or multi-standard mode.As well as “UE” and “terminal device”, the term “mobile device” is usedinterchangeably in the following description, and it will be appreciatedthat such a device does not necessarily have to be mobile in the sensethat it is carried by a user. Instead, the term “mobile device”, as with“terminal device” encompasses any device that is capable ofcommunicating with communication networks that operate according to oneor more mobile communication standards, such as GSM, UMTS, LTE, etc.

A cell is associated with a radio access network (RAN) node, where a RANnode comprises in a general sense any node transmitting radio signals inthe downlink (DL) to a terminal device and/or receiving radio signals inthe uplink (UL) from a terminal device. Some example RAN nodes, or termsused for describing RAN nodes, are base station, eNodeB, eNB, NodeB,macro/micro/pico/femto radio base station, home eNodeB (also known asfemto base station), relay, repeater, sensor, transmitting-only radionodes or receiving-only radio nodes. A RAN node may operate or at leastperform measurements in one or more frequencies, carrier frequencies orfrequency bands and may be capable of carrier aggregation. It may alsobe a single-radio access technology (RAT), multi-RAT, or multi-standardnode, e.g., using the same or different base band circuitry fordifferent RATs.

It should be noted that unless otherwise indicated, the use of thegeneral term “network node” as used herein refers to a RAN node, such asa base station, an eNodeB, a network node in the RAN responsible forresource management, such as a radio network controller (RNC), a corenetwork node, such as a mobility management entity (MME) or SGW, or aWLAN Access Point (AP).

The signalling described is either via direct links or logical links(e.g. via higher layer protocols and/or via one or more network nodes).For example, signalling from a coordinating node may pass anothernetwork node, e.g., a radio node.

FIG. 1 shows an example diagram of an evolved UMTS Terrestrial RadioAccess Network (EUTRAN) architecture as part of an LTE-basedcommunications system 2. Nodes in the core network 4 include one or moreMobility Management Entities (MMEs) 6, a key control node for the LTEaccess network, and one or more Serving Gateways (SGWs) 8 which routeand forward user data packets while acting as a mobility anchor. Theycommunicate with base stations 10 in the RAN referred to in LTE as eNBsor eNodeBs, over an interface, for example an S1 interface. The eNBs 10can include the same or different categories of eNBs, e.g. macro eNBs,and/or micro/pico/femto eNBs. The eNBs 10 communicate with each otherover an interface, for example an X2 interface. The S1 interface and X2interface are defined in the LTE standard. A UE 12 can receive downlinkdata from and send uplink data to one of the base stations 10 with thatbase station 10 being referred to as the serving base station of the UE12. An access point (AP) 14 that is part of a WLAN is also shown in FIG.1, although it will be appreciated that the WLAN and AP 14 are not partof the EUTRAN architecture. As is known in the art, the UE 12 may becapable of aggregating multiple carriers from a single eNB 10 ormultiple eNBs 10, and in accordance with certain embodiments, the UE 12is capable of aggregating a carrier from the LTE network 2 with acarrier from the WLAN AP 14.

FIG. 2 shows a terminal device 12 or user equipment (UE) that can beadapted for use in one or more of the non-limiting example embodimentsdescribed. The terminal device 12 comprises a processing unit 30 thatcontrols the operation of the terminal device 12. The processing unit 30is connected to a receiver or a transceiver 32 (which comprises areceiver and a transmitter) with associated antenna(s) 34 which are usedto receive signals from or both transmit signals to and receive signalsfrom two different types of radio access network (i.e. two radio accessnetworks that are operating according to different radio accesstechnologies, RATs), such as RAN node 10 in the LTE network 2 and accesspoint (AP) 14 in a WLAN. The terminal device 12 also comprises a memoryunit 36 that is connected to the processing unit 30 and that storescomputer program code and other information and data required for theoperation of the terminal device 12.

FIG. 3 shows a RAN node 10 (for example a base station, NodeB or aneNodeB) that can be adapted for use in example embodiments described.The RAN node 10 comprises a processing unit 40 that controls theoperation of the base station 10. The processing unit 40 is connected toa transmitter or a transceiver 42 (which comprises a receiver and atransmitter) with associated antenna(s) 44 which are used to transmitsignals to, and receive signals from, terminal devices 12 in the network2. The RAN node 10 also comprises a memory unit 46 that is connected tothe processing unit 40 and that stores computer program code and otherinformation and data required for the operation of the RAN node 10. TheRAN node 10 also includes components and/or circuitry 48 for allowingthe RAN node 10 to exchange information with other RAN nodes 10 (forexample via an X2 interface) and components and/or circuitry 49 forallowing the RAN node 10 to exchange information with nodes in the corenetwork 4 (for example via the S1 interface). It will be appreciatedthat RAN nodes for use in other types of network (e.g. UTRAN or WCDMARAN) will include similar components to those shown in FIG. 3 andappropriate interface circuitry 48, 49 for enabling communications withthe other network nodes in those types of networks (e.g. other basestations, mobility management nodes and/or nodes in the core network).

FIG. 4 shows a core network node 6, 8 that can be adapted for use in theexample embodiments described. The node 6, 8 comprises a processing unit50 that controls the operation of the node 6, 8. The processing unit 50is connected to components and/or circuitry 52 for allowing the node 6,8 to exchange information with RAN nodes 10 with which it is associated(which is typically via the S1 interface). The node 6, 8 also comprisesa memory unit 56 that is connected to the processing unit 50 and thatstores computer program code and other information and data required forthe operation of the node 6, 8.

FIG. 5 shows a WLAN AP 14 that can be adapted for use in the exampleembodiments described. The AP 14 comprises a processing unit 60 thatcontrols the operation of the AP 14. The processing unit 60 is connectedto a transmitter or a transceiver 62 (which comprises a receiver and atransmitter) with associated antenna(s) 64 which are used to transmitsignals to, and receive signals from, terminal devices 12. The AP 14also comprises a memory unit 66 that is connected to the processing unit60 and that stores computer program code and other information and datarequired for the operation of the AP 14. The AP 14 also includescomponents and/or circuitry 68 for connecting the AP 14 to a telephoneline or other broadband connection.

It will be appreciated that only the components of the terminal device12, RAN node 10, core network node 6, 8 and AP 14 required to explainthe embodiments presented herein are illustrated in FIGS. 2, 3, 4 and 5.

As noted above, 3GPP is currently working on specifying afeature/mechanism for WLAN/3GPP Radio interworking which improvesoperator control with respect to how a UE performs access selection andtraffic steering between 3GPP and WLANs belonging to the operator or itspartners. The two main options for performing traffic steering between3GPP and WLAN networks are described below.

The first option, which is termed a ‘threshold based approach’ is basedon conditions and thresholds provided to the terminal device 12 by afirst RAT (e.g. a network operating according to a first RAT, such as a3GPP-specified RAT or WLAN) which dictates in which situations theterminal device 12 should steer traffic from/to a second RAT (e.g. anetwork operating according to a second RAT, such as another3GPP-specified RAT or WLAN). This option is applicable regardless ofwhether a connection exists between the terminal device 12 and the firstRAT, e.g. both when a terminal device 12 is in RRC_CONNECTED mode in3GPP LTE and when the terminal device 12 is in IDLE mode in LTE.

For example, a rule comprising thresholds and conditions could take theform of Example 1 below where the parameter values threshold1,threshold2, threshold3 and threshold4 are provided to the terminaldevice 12 by the 3GPP network 2 (i.e. a network node in the 3GPP network2 such as an eNodeB, NodeB or radio network controller (RNC)).

  if (3GPP signal < threshold1) && (WLAN signal > threshold2) {  steerTrafficToWLAN( ); } else if (3GPP signal > threshold3) (WLANsignal < threshold4) {   steerTrafficTo3gpp( ); }

Example 1

If the 3GPP signal measured by the terminal device 12 is belowthreshold1 and the WLAN signal measured by the terminal device 12 isabove threshold2, the mechanism provides that a timer is started, and ifthe signals continue to satisfy the thresholds until expiry of thetimer, the terminal device 12 steers traffic to WLAN 14. Otherwise, ifthe 3GPP signal is above threshold3 or the WLAN signal is belowthreshold4, the timer is started and if the signals continue to satisfythose thresholds the rule provides that the terminal device 12 shallsteer traffic to the 3GPP network 2.

The term ‘3GPP signal’ herein could mean the signal transmitted by aradio network node belonging to a 3GPP RAT, e.g. a node in a LTE, HSPA,GSM etc. network, and/or it could be the quality of such a signal. Theterm ‘WLAN signal’ herein could mean the signal transmitted by a radionetwork node belonging to WLAN, e.g. an access point (AP) etc., and/orit could be the quality of such a signal. Examples of measurements of3GPP signals include are reference signal received power (RSRP) andreference signal received quality (RSRQ) in LTE or common pilot channel(CPICH) received signal code power (RSCP) and CPICH Ec/No in HSPA.Examples of measurements of WLAN signals are Received Signal StrengthIndicator (RSSI), Received Channel Power Indicator (RCPI), ReceivedSignal to Noise Indicator (RSNI), etc.

In the second option, which is termed a ‘traffic steering command basedapproach’, a first RAT, e.g. a 3GPP RAT (a network operating accordingto a 3GPP RAT), controls a terminal device's connection to a second RAT,e.g., a WLAN. In a first implementation, the approach providesmeasurement reporting from the terminal device to the 3GPP network andthe 3GPP network sending traffic steering commands that order theterminal device to steer traffic from/to the second RAT. In a secondimplementation, a traffic steering command may be sent without requiringmeasurement reporting to be done first (in which case the first RATevaluates the parameters and/or rules based on information available tothe first RAT). To send the traffic steering command it is required thata connection is established between the terminal device 12 and the firstRAT, e.g. for a terminal device 12 to be in RRC_CONNECTED mode in 3GPPLTE if LTE should be used in sending traffic steering commands.

The first implementation of this approach is based on three messages andsome associated procedures that allow the 3GPP network 2 to determinewhen a terminal device 12 should associate with a WLAN 14 or, moregenerally, to a network operating according to a second (possiblydifferent) radio access technology (RAT). The procedure is illustratedin FIG. 6. The first message, a reporting configuration message (message1), is sent from the 3GPP network (3GPP radio access network (RAN) node10) to the terminal device 12 and configures the terminal device 12 witha set of criteria or parameters (e.g. a set of conditions and/orthresholds) for enabling, detecting, or performing measurements over thesecond network (WLAN 14).

One possible set of criteria contained in one possible reportingconfiguration message is as follows:

-   -   Received signal strength indicator (RSSI) in WLAN>X    -   Reference signal received power (RSRP) in 3GPP<Y and/or    -   BSS load<Z

Other metrics that can be considered included RCPI, RSNI, RSRP, uplink(UL) and/or downlink (DL) backhaul rate, etc.

The terminal device 12 subsequently sends a terminal report, message 2,to the 3GPP network 10, when the criteria given in the first message(message 1) have been fulfilled. The 3GPP network 10 evaluates thecontent of the terminal report, along with any other reports orinformation that the network 10 may have available, such as backhaulcongestion, delay, subscription information and interference, anddetermines whether or not to steer the terminal device's traffic to WLAN14. The third message (message 3), a traffic steering message orcommand, is an indicator sent from the 3GPP network 10 to the terminaldevice 12 that the terminal device 12 should steer all or a subset ofits traffic to WLAN 14. The traffic steering message may indicate aspecific target access point (AP) in the WLAN 14, such as a prioritisedAP or WLAN or it could just be a command telling the terminal device 12to steer its traffic to WLAN 14 and the terminal device 12 and WLAN 14determine which particular AP should be used. The traffic steeringmessage may also indicate which traffic should be steered to WLAN 14and/or which traffic should be kept in the 3GPP network 10.

In some implementations it is possible that both of the abovealternatives can be used. For example the threshold based approach canbe used when no connection exists between the terminal device 12 and thecontrolling RAT and the traffic steering command based approach can beused when a connection exists.

For Release 12, 3GPP has decided to implement a solution similar to thethreshold based approach described above, where the RAN providesassistance parameters that helps the UE in taking the access selectionand/or traffic steering decision. A general description of the agreedsolution for LTE that has been incorporated into the relevant 3GPPspecification (3GPP TS 36.300 v12.2.0 (2014-06)—Evolved UniversalTerrestrial Radio Access (E-UTRA) and Evolved Universal TerrestrialRadio Access Network (E-UTRAN); Overall description; Stage 2) is set outbelow. A similar solution has been agreed for UMTS and will beincorporated into the relevant 3GPP specification (3GPP TS25.300—Universal Terrestrial Radio Access Network (UTRAN): Generaldescription; Stage 2):

This section describes the mechanisms to support traffic steeringbetween E-UTRAN and WLAN. 23.6.1 General principles This version of thespecification supports E-UTRAN assisted UE based bi-directional trafficsteering between E-UTRAN and WLAN for UEs in RRC_IDLE and RRC_CONNECTED.E-UTRAN provides assistance parameters via broadcast and dedicated RRCsignalling to the UE. The RAN assistance parameters may include E-UTRANsignal strength and quality thresholds, WLAN channel utilizationthresholds, WLAN backhaul data rate thresholds, WLAN signal strength andquality thresholds and Offload Preference Indicator (OPI). E-UTRAN canalso provide a list of WLAN identifiers to the UE via broadcastsignalling. WLANs provided by E-UTRAN may include an associatedpriority. The UE uses the RAN assistance parameters in the evaluationof:  - Traffic steering rules defined in TS 36.304 [11]; or  - ANDSFpolicies defined in TS 24.312 [58] for traffic steering decisionsbetween E-UTRAN and WLAN as specified in TS 23.402[19]. The OPI is onlyused in ANDSF policies as specified in TS 24.312 [58]. WLAN identifiersare only used in traffic steering rules defined in TS 36.304 [11]. Ifthe UE is provisioned with ANDSF policies it shall forward the receivedRAN assistance parameters to upper layers, otherwise it shall use themin the traffic steering rules defined in section 23.6.2 and TS 36.304[11]. The traffic steering rules defined in section 23.6.2 and TS 36.304[11] are applied only to the WLANs of which identifiers are provided bythe E-UTRAN. The UE in RRC_CONNECTED shall apply the parameters obtainedvia dedicated signalling if such have been received from the servingcell; otherwise, the UE shall apply the parameters obtained viabroadcast signalling. The UE in RRC_IDLE shall keep and apply theparameters obtained via dedicated signalling, until cell reselection ora timer has expired since the UE entered RRC_IDLE upon which the UEshall apply the parameters obtained via broadcast signalling. In thecase of RAN sharing, each PLMN sharing the RAN can provide independentsets of RAN assistance parameters. 23.6.2 Access network selection andtraffic steering rules The UE indicates to upper layers when (and forwhich WLAN identifiers along with associated priorities, if any) accessnetwork selection and traffic steering rules defined in TS 36.304 [11]are fulfilled. The selection among WLAN APs that fulfil the accessnetwork selection and traffic steering rules is up to UE implementation.When the UE applies the access network selection and traffic steeringrules defined in TS 36.304 [11], it performs traffic steering betweenE-UTRAN WLAN with APN granularity. User preference takes precedence (FFSwhether it does not apply to particular scenarios).

An exemplary set of access network selection and/or traffic steeringrules and parameters is shown below. This text is not yet finalised, andmay be modified before it is incorporated into a specification. In thecase of LTE, it will be included in 3GPP TS 36.304—Evolved UniversalTerrestrial Radio Access (E-UTRA); User Equipment (UE) procedures inidle mode. A similar set of rules and parameters will be finalised forUMTS and will be added to 3GPP TS 25.304—User Equipment (UE) proceduresin idle mode and procedures for cell reselection in connected mode.

5.x Access network selection and traffic steering between E-UTRAN andWLAN 5.x.1 RAN assistance parameter handling in RRC_IDLE RAN assistanceparameters may be provided to the UE in SystemInformationBlockType17 orin the RRCConnectionReconfiguration message. RAN assistance parametersreceived in SystemInformationBlockType17 are valid only if the UE iscamped on a suitable cell. The UE shall discard the RAN assistanceparameters upon cell reselection. Upon T350 expiry, the UE shall discardthe RAN assistance parameters received in theRRCConnectionReconfiguration message and apply the RAN assistanceparameters received in SystemInformationBlockType17. The upper layers inthe UE shall be notified whenever changes in the current RAN assistanceparameters occur. 5.x.2 Access network selection and traffic steeringrules The rules in this sub-clause are only applicable for a WLAN forwhich an identifier has been signaled to the UE by E-UTRAN and the UE iscapable of traffic steering between E-UTRAN and WLAN. Coexistence withANDSF based WLAN selection and traffic steering methods on the UE isbased on mechanism described in TS 23.402 [x1]. The rules refer to thefollowing quantities: Editor's note: “UE is capable of traffic steeringbetween E-UTRN and WLAN” should be replaced with a name for this featureChannelUtilizationWLAN WLAN channel utilization as defined in subclause8.4.2.30 in [x2]. BackhaulRateDIWLAN WLAN DLBandwidth as defined insubclause 9.1.2 in [x3]. BackhaulRateUIWLAN WLAN ULBandwidth as definedsubclause 9.1.2 in in [x3]. RCPI WLAN RCPI as defined in subclause8.4.2.40 in [x2]. RSNI WLAN RSNI as defined in subclause 8.4.2.43 in[x2]. RSRPmeas Qrxlevmeas in RRC IDLE, and PCell RSRP in RRC CONNECTEDas defined in TS 36.331 [3]. RSRQmeas Qqualmeas in RRC IDLE, and PCellRSRQ in RRC CONNECTED as defined in TS 36.331 [3]. The upper layers inthe UE shall be notified when and for which WLAN identifiers (out of thelist in RAN parameters in subclause 5.x.3) the following conditions 1and 2 for steering traffic from E-UTRAN to WLAN are satisfied for a timeinterval Tsteering_(WLAN): 1. In the E-UTRAN serving cell:  RSRPmeas <Thresh_(ServingOffloadWLAN, LowP;) or  RSRQmeas <Thresh_(ServingOffloadWLAN, LowQ;) 2. In the target WLAN: ChannelUtilizationWLAN < Thresh_(ChUtilWLAN, Low); and BackhaulRateDIWLAN > Thresh_(BackhRateDLWLAN, High); and BackhaulRateUIWLAN > Thresh_(BackhRateULWLAN, High); and  RCPI >Thresh_(RCPIWLAN, High); and  RSNI > Thresh_(RSNIWLAN, High); The UEshall exclude the evaluation of a measurement for which a threshold hasnot been provided. The UE shall evaluate the E-UTRAN conditions on PCellonly. If not all metrics related to the provided thresholds can beacquired for a WLAN, the UE shall exclude that WLAN from the evaluationof the above rule. The notification to the upper layers shall alsoinclude the priorities for the WLAN identifiers if provided by theE-UTRAN. The upper layers in the UE shall be notified when the followingconditions 3 or 4 for steering traffic from WLAN to E-UTRAN aresatisfied for a time interval Tsteering_(WLAN): 3. In the source WLAN: ChannelUtilizationWLAN > Thresh_(ChUtilWLAN, High); or BackhaulRateDIWLAN < Thresh_(BackhRateDLWLAN, Low); or BackhaulRateUIWLAN < Thresh_(BackhRateULWLAN, Low); or  RCPI <Thresh_(RCPIWLAN, Low); or  RSNI < Thresh_(RSNIWLAN, Low); 4. In thetarget E-UTRAN cell:  RSRPmeas > Thresh_(ServingOffloadWLAN, HighP;) and RSRQmeas > Thresh_(ServingOffloadWLAN, HighQ;) The UE shall exclude theevaluation of a measurement for which a threshold has not been provided.The UE shall evaluate the E-UTRAN conditions on PCell only. 5.x.3 RANassistance parameters definition The following RAN assistance parametersfor access network selection and traffic steering between E-UTRAN andWLAN may be provided: Thresh_(ServingOffloadWLAN, LowP) This specifiesthe RSRP threshold (in dBm) used by the UE for traffic steering to fromE-UTRAN to WLAN. Thresh_(ServingOffloadWLAN, HighP) This specifies theRSRP threshold (in dBm) used by the UE for traffic steering from WLAN toE-UTRAN. Thresh_(ServingOffloadWLAN, LowQ) This specifies the RSRQthreshold (in dB) used by the UE for traffic steering from E- UTRAN toWLAN. Thresh_(ServingOffloadWLAN, HighQ) This specifies the RSRQthreshold (in dB) used by the UE for traffic steering from WLAN toE-UTRAN. Thresh_(ChUtilWLAN, Low) This specifies the WLAN channelutilization (BSS load) threshold used by the UE for traffic steeringfrom E-UTRAN to WLAN. Thresh_(ChUtilWLAN, High) This specifies the WLANchannel utilization (BSS load) threshold used by the UE for trafficsteering from WLAN to E-UTRAN. Thresh_(BackhRateDLWLAN, Low) Thisspecifies the backhaul available downlink bandwidth threshold used bythe UE for traffic steering from WLAN to E-UTRAN.Thresh_(BackhRateDLWLAN), High This specifies the backhaul availabledownlink bandwidth threshold used by the UE for traffic steering fromE-UTRAN to WLAN. Thresh_(BackhRateULWLAN, Low) This specifies thebackhaul available uplink bandwidth threshold used by the UE for trafficsteering from WLAN to E-UTRAN. Thresh_(BackhRateULWLAN, High) Thisspecifies the backhaul available uplink bandwidth threshold used by theUE for traffic steering from E-UTRAN to WLAN. Thresh_(RCPIWLAN, Low)This specifies the RCPI threshold used by the UE for traffic steeringfrom WLAN to E- UTRAN. Thresh_(RCPIWLAN, High) This specifies the RCPIthreshold used by the UE for traffic steering from E-UTRAN to WLAN.Thresh_(RSNIWLAN, Low) This specifies the RSNI threshold used by the UEfor traffic steering from WLAN to E- UTRAN. Thresh_(RSNIWLAN, High) Thisspecifies the RSNI threshold used by the UE for traffic steering fromE-UTRAN to WLAN. Tsteering_(WLAN) This specifies the timer valueTsteering_(WLAN) during which the rules should be fulfilled beforestarting traffic steering between E-UTRAN and WLAN. WLAN identifiersOnly the SSIDs, BSSIDs or HESSIDs which are provided in this parametershall be considered for traffic steering between E-UTRAN and WLAN basedon the rules in this subclause. WLAN priorities WLAN priorities may beprovided for WLANs included in the WLAN identifiers.

As seen above, in this mechanism the terminal device 12 applies a timer(Tsteering_(WLAN)) when the parameters and/or rules are satisfied. Whenthe parameters and/or rules have been fulfilled for a timeTsteering_(WLAN) the terminal device 12 shall indicate to higher layers(in the terminal device 12) that traffic steering shall be executed andprocedures in higher layers are then used to execute the trafficsteering.

As noted above, a problem exists with the use of the timer in the agreedmechanism, and the alternative techniques described above, in that it ispossible that, once the timer is started in response to the parametersand/or rules being met, the parameters and/or rules may change or beupdated while the timer is running (i.e. before the timer expires). Ifthe timer is allowed to continue running, it may be that the terminaldevice 12 executes the change in access network or traffic steeringearlier than configured by the network. This use of the timer may resultin ping-ponging of the terminal device 12 between the RATs, whichimpairs user experience due to interruptions, increases signallingoverhead, and also leads to terminal device 12 behaviour that is notexpected by the network.

Therefore, the techniques described herein provide that the operation ofthe timer is adjusted when there are new or updated parameters and/orrules or where new or updated parameters and/or rules may be expected tobe received. In this way, the risk of undesirable behaviour from theterminal device 12 is reduced.

Although the techniques are primarily described with reference to accessnetwork selection and/or traffic steering between a 3GPP network and aWLAN, it will be appreciated that the techniques are more broadlyapplicable to access network selection and/or traffic steering betweenany two networks that are operating according to different radio accesstechnologies (e.g. between a 3GPP network and a non-3GPP network otherthan WLAN, such as Worldwide Interoperability for Microwave Access(WiMAX), or between two different 3GPP networks). Moreover, it will beappreciated that the techniques can also be used in extended accessnetwork selection and/or traffic steering mechanisms that determinewhether a terminal device can aggregate carriers across the multiplenetworks (e.g. aggregate a carrier in 3GPP and a carrier in WLAN for aparticular traffic flow (e.g. video stream)).

As noted below, the techniques described herein can be applied to eitherof the threshold-based and traffic steering command-based approachesdescribed above, as well as to other approaches in which parametersand/or rules are evaluated in order to take an access network selectionand/or traffic steering and/or aggregation decision and the parametersand/or rules are required to be satisfied for a predetermined timeperiod before the decision is implemented.

A method of operating an apparatus in a first network operatingaccording to a first RAT is shown in FIG. 7. Depending on the specificimplementation, the apparatus may be the terminal device 12 or a node inthe first network (e.g. a node in the RAN, such as an eNB 10, or a nodein the core network, such as an MME where the first network is a 3GPPnetwork, or a WLAN AP 14 where the first network is a WLAN).

In a first step of the method, step 101, the apparatus evaluatesparameters and/or rules as part of an access network selection and/ortraffic steering and/or traffic aggregation procedure for a particularterminal device 12 with respect to the first network (e.g. 3GPP network)and/or a second network that is operating according to a second(different) RAT (e.g. WLAN).

In some implementations this step can comprise making measurements ofsignals from the first network and/or second network, determining valuesfor one or more signal-related parameters, and comparing the values tothe parameters and/or rules (where the parameters can comprise thresholdvalues and/or conditions) to determine if the parameters and/or ruleshave been satisfied. In other implementations this step can comprisereceiving values for one or more signal-related parameters from aterminal device and comparing the values to the parameters and/or rulesto determine if the parameters and/or rules have been satisfied.

In some embodiments the signal-related parameters can comprise, forexample, any of reference signal received power (RSRP) and referencesignal received quality (RSRQ) in LTE or common pilot channel (CPICH)received signal code power (RSCP) and CPICH Ec/No in HSPA, ReceivedSignal Strength Indicator (RSSI), Received Channel Power Indicator(RCPI) or Received Signal to Noise Indicator (RSNI) in Wi-Fi.

Then, in step 103, a timer is started if the parameters and/or rules aresatisfied. In other words, a timer is started if the evaluation of theparameters and/or rules in step 101 indicates that the terminal device12 that is associated with one or both of the first network and secondnetwork (where ‘associated with’ means that the terminal device 12 isauthenticated with or otherwise connected to) is to access the othernetwork (i.e. the one of the first and second network that the terminaldevice 12 is not currently accessing) and/or steer traffic to the othernetwork and/or aggregate traffic across the first and second network(e.g. split a particular traffic flow, service, bearer or applicationacross a carrier in each of the first network and second network). Asindicated above, in the case of the 3GPP-agreed access network selectionand/or traffic steering mechanism, the timer or predetermined timeperiod is denoted Tsteering_(WLAN).

Next, if an event occurs prior to expiry of the timer that changes anyof the parameters and/or rules evaluated in step 101, or that maypotentially change any of the parameters and/or rules evaluated in step101, the operation of the timer is adjusted (step 105).

Adjusting the operation of the timer can comprise any action thatresults in the timing of the implementation of the access networkselection and/or traffic steering and/or traffic aggregation decisionfrom step 101 being different to allowing the timer to continueunadjusted. This adjustment of the operation of the timer reduces theoccurrence of ping-ponging of the terminal device 12 between the RATs,which reduces the chance of impairing the user experience due tointerruptions, avoids additional signalling overhead, and also reducesthe risk of terminal device 12 behaviour that is not expected by thenetwork.

In particular embodiments, adjusting the operation of the timer cancomprise any of:

stopping the timer (which can include stopping the timer so that itcannot be resumed later), disabling the timer, suspending or pausing thetimer (which can include pausing the timer so that it can be resumedfrom the paused value later), and restarting the timer (which caninclude resetting the elapsed time to zero or resetting the timer to theinitial value).

For example, if the terminal device 12 has evaluated a rule in step 101and determined that according to current parameters the conditions forsteering traffic to a WLAN are fulfilled, the terminal device 12 shouldthen perform traffic steering to the WLAN after the conditions have beenfulfilled for a time Tsteering_(WLAN). However, the terminal device 12may, before Tsteering_(WLAN) has expired, receive updated parametersfrom the 3GPP network. According to the techniques described herein, theterminal device 12 would in that case stop, suspend, disable or restartthe timer Tsteering_(WLAN) (step 105).

As described in more detail below, a change in the parameters and/orrules can be signalled to the apparatus by the first network (e.g. 3GPPnetwork) or second network (e.g. WLAN). The change in the parametersand/or rules may be signalled to the apparatus from a node in the firstnetwork (e.g. eNB 10 or MME 6) or a node in the second network (e.g.WLAN AP 14), and, in the case that the apparatus is the terminal device12, may be communicated to the terminal device 12 via broadcast ordedicated signalling.

A change in the parameters and/or rules might occur as the conditions(e.g. load) in the first and/or second network change (in which case anetwork may change the parameters in the access network selection and/ortraffic steering and/or traffic aggregation mechanism in order toencourage more traffic to a particular network). In this case, step 105can be performed on receipt of the new or updated parameters and/orrules.

A change in the parameters and/or rules may also occur if the particularparameters and/or rules to be evaluated in step 101 are changed (i.e.changed to different ones of previously received or determinedparameters and/or rules). For example, only a subset of a set ofparameters and/or rules may be evaluated as part of the access networkselection and/or traffic steering and/or traffic aggregation procedurein step 101, and it is possible that the subset of parameters and/orrules to be evaluated can be changed over time. One example where thismay occur is in carrier aggregation where there are sets of parametersand/or rules for each carrier that is being aggregated by a terminaldevice, and all sets are received when the aggregation starts. Aparticular set of parameters and/or rules (e.g. for one carrier) isselected for evaluation in step 101, but subsequently the selected setis changed (e.g. as the particular aggregated carriers change). Thischange in the evaluated parameters and/or rules will result in theadjustment of the operation of the timer in step 105.

A change in the parameters and/or rules may also occur following achange in the serving cell of the terminal device 12 (e.g. following ahandover or cell reselection) if the serving cells have differentparameter values (and/or rules) to each other. Parameters and/or rulesfor a new serving cell of a terminal device 12 may not be signalled to aterminal device 12 or other apparatus as soon as the terminal device 12starts being served by the new cell, and may take some time to becommunicated. This is particularly the case where the parameters and/orrules are communicated in a system information broadcast (SIB) message,since a terminal device 12 may not read the SIB very frequently.Therefore, in some embodiments the occurrence of a handover orreselection event at the terminal device 12 can be used as a trigger foradjusting the operation of the timer in step 105 (i.e. since a handoveror cell reselection event indicates that there is a potential change tothe parameters and/or rules).

In some embodiments, the step of adjusting (step 105) is performedwhenever the parameters and/or rules used for the terminal device 12 areupdated or changed.

In other embodiments, the step of adjusting (step 105) is performedwhenever the parameters and/or rules used for the terminal device 12 areupdated or changed and the updated or changed parameters and/or rulesare different from the previous parameters and/or rules (the onesevaluated in step 101) or different by more than a threshold amount.This embodiment can further comprise the steps of performing acomparison of the updated parameters and/or rules and the evaluatedparameters and/or rules and, where some difference in the parametersand/or rules is permitted, comparing the differences in the parametersand/or rules to one or more thresholds. The result of the comparison ofthe differences is then used to determine whether to adjust theoperation of the timer. If the differences in the parameters and/orrules is less than the threshold (e.g. the parameters and/or rules areidentical), then the timer can be allowed to continue.

For example, the value for an RSRP threshold provided in the updatedparameters and/or rules and the value for the RSRP threshold provided inthe evaluated parameters and/or rules are compared, and the differencein the threshold values compared to a threshold to determine if thedifference is too significant to allow the timer to continue running andthe access network selection and/or traffic steering and/or trafficaggregation to be implemented.

In some embodiments, after the operation of the timer is adjustedfollowing a cell change by the terminal device 12 (e.g. the timer issuspended or paused), the new parameters and/or rules for the newserving cell can be compared to the previous parameters and/or rules(once the new parameters and/or rules are received). If the newparameters and/or rules are identical to the previous parameters and/orrules, or differ by less than a threshold, then the method can furthercomprise the step of resuming the timer (i.e. restarting the timer fromthe point that it was suspended or paused). A benefit of this embodimentis that if the terminal device 12 is moving between two cells for whichthe parameters are identical (or which differ by less than a threshold),it might not be suitable for the terminal device 12 to restart the timerfrom the beginning (which may occur as soon as the new parameters and/orrules are evaluated) as this will delay the implementation of the accessnetwork selection and/or traffic steering and/or traffic aggregationdecision. This is especially true for cases where the timer duration isconfigured to be quite long. If the parameters and/or rules are notidentical, or not within the threshold amount of each other, the timercould be left in the suspended or paused state, or it could be stoppedor disabled to prevent or abort the previous decision on access networkselection and/or traffic steering and/or aggregation from beingimplemented.

In another embodiment, after a serving cell change and before anyupdated parameters and/or rules are received, the timer can be allowedto continue running. However, if the timer expires prior to updatedparameters and/or rules being received, the implementation of the accessnetwork selection and/or traffic steering and/or traffic aggregationdecision can be prevented (i.e. aborted) or delayed. Once the updatedparameters and/or rules are received, they can be compared to theprevious parameters and/or rules as described for the above embodiments,and if they are identical (or within a threshold amount), then thepreviously determined decision can be implemented. If they are notidentical or within the threshold amount, the determined decision can becancelled (i.e. not implemented).

In some embodiments, the particular way in which the operation of thetimer is to be adjusted in step 105 is preconfigured in the apparatus.In some embodiments, the apparatus may be preconfigured to adjust theoperation of the timer differently depending on the cause for the changein the parameters and/or rules (e.g. due to cell change, etc.). In otherembodiments, the apparatus may receive an indication from a network nodein the network that indicates the way in which the operation of thetimer is to be adjusted. This is illustrated in FIG. 8. Thus, in step111, an indication is sent from the network node to the apparatus thatis, or is to, perform the access network selection and/or trafficsteering and/or traffic aggregation procedure, the indication indicatingthe way in which the operation of the timer is to be adjusted in theevent that there is a change or potential change in the parametersand/or rules that are evaluated as part of the procedure. In someembodiments, the indication may indicate the way in which the operationof the timer is adjusted for different causes for the change in theparameters and/or rules (e.g. perform one type of adjustment on cellchange and a different type of adjustment when the network updates theparameters and/or rules). Alternatively, multiple indications can beprovided, each indicating the way in which the operation of the timer isadjusted for a particular cause in for the change in the parametersand/or rules. In some embodiments, the indication may also indicate thereasons or events for which the operation of the timer is to be adjusted(e.g. cell change).

Upon receiving an indication from the network the comparison describedin this context above may also consist of the terminal onlyevaluating/comparing an old configuration with a new if the indicationfrom the NW indicates, “continue” e.g. while a timer is running. Theterminal may upon this indication from network, continue using thestored parameters of a (previous) configuration in the same cell.

The indication in this context may be included as part of, or otherwiserelated to, new parameters/configuration in either system information ordedicated signalling.

It will be appreciated that the apparatus may only consider theparameters and/or rules to have changed and thus trigger an adjustmentto the operation of the timer if certain ones of the parameters or ruleshave changed. For example, the parameters and/or rules may not beconsidered to have changed within the meaning of step 105 if, forexample, only parameters such as identifiers for the access points (e.g.WLAN identifiers) that are used in the access network selection and/ortraffic steering and/or traffic steering procedure have changed. In someembodiments, the parameters and/or rules may only be considered to havechanged if one or more of the thresholds and/or conditions have changed(or changed by more than a threshold amount).

In some embodiments the apparatus can consider the current state of theterminal device 12 with respect to the second network (e.g. is theterminal device steering traffic to the second network) when evaluatingwhether to adjust the operation of the timer (e.g. stop, restart orsuspend the timer). For example, the timer may be stopped, restarted orsuspended only if the terminal device 12 is not currently steeringtraffic to the second network (e.g. WLAN), but if the terminal devicehas traffic carried over the second network the operation of the timerwould not be adjusted.

After taking a decision to access one of the first and second network,to steer traffic to one of the first and second network, or to aggregatea traffic flow over both networks, and on expiry of the timer, themethod in FIG. 7 further comprises the step of implementing thatdecision and causing the terminal device 12 to steer traffic to one ofthe first and second network, or to aggregate a traffic flow over bothnetworks as appropriate. In implementations where the apparatus is theterminal device 12, this step can comprise the terminal device 12establishing (or maintaining) the appropriate connections to the firstand/or second networks and sending and/or receiving the appropriatetraffic over that or those networks. In implementations where theapparatus is a network node 10, 14, this step can comprise sending atraffic steering command or other signal to the terminal device 12instructing the terminal device 12 to establish (or maintain) theappropriate connections to the first and/or second networks.

In the implementations where the apparatus is the terminal device 12,prior to step 101, the method can further comprise the step of receivingthe parameters and/or rules from a network node 10, 14 in a network withwhich the terminal device 12 is associated. Thus, the terminal device 12can receive the parameters and/or rules from an eNB 10 in the 3GPPnetwork 2 and/or from a Wi-Fi AP 14. In this implementation the methodcan also comprise the step of measuring signals from the first networkand/or second network (and determining values of one or more parametersfrom the measured signals) and the step of evaluating (step 101)comprises comparing the measurements or values to thresholds and/orconditions in the received parameters and/or rules.

In the implementations where the apparatus is a network node 10, 14, themethod can further comprise determining the parameters and/or rules thatare to be evaluated in step 101, and sending the parameters and/or rulesto the terminal device 12. In some embodiments the rules can bespecified in a standard (e.g. a 3GPP standard), whereas in otherembodiments the rules can be preconfigured by the network operator ordynamically determined based on, for example, the load in the firstand/or second network. The method can further comprise receivingmeasurements of signals from the first network and/or second networkfrom the terminal device 12, or receiving parameter values derived frommeasurements of signals received at the terminal device 12.

The flow chart in FIG. 9 illustrates a specific method of operating anapparatus according to the techniques described herein. In this method,the second network is a WLAN. In a first step, step 121, parametersand/or rules comprising thresholds and conditions are evaluated andfound to be fulfilled so traffic can be steered to WLAN. As theconditions are fulfilled, the time-to-trigger timer (having durationTsteering_(WLAN)) is started.

At some time prior to the expiry of Tsteering_(WLAN), new parameters(specifically new threshold values) relevant to the traffic steeringparameters and/or rules are received (step 125). The new thresholds arecompared to the previous thresholds to determine if the thresholds areconsidered to have changed (step 127).

If the threshold values are not considered to have changed (e.g. theyare identical), then the timer is allowed to continue running (step129), and if the timer expires with the conditions for traffic steeringremaining fulfilled, the steering of traffic to WLAN is performed.

If the threshold values are considered to have changed, then it isdetermined if the threshold values have changed by more than a threshold(step 131). If they have not changed by more than a threshold, the timeris allowed to continue running (step 129). If they have changed by morethan a threshold, the timer is stopped (step 133) and the traffic is notsteered to WLAN. It will be appreciated that there may be a singlethreshold that is used for each threshold value (e.g. a thresholdpercentage change, e.g. 10%), or there may be a respective changethreshold for each threshold value (e.g. there may be one threshold forchanges in RSSI and another, different threshold, for changes in BSSload).

Modifications and other variants of the described embodiment(s) willcome to mind to one skilled in the art having the benefit of theteachings presented in the foregoing descriptions and the associateddrawings. Therefore, it is to be understood that the embodiments) is/arenot to be limited to the specific examples disclosed and thatmodifications and other variants are intended to be included within thescope of this disclosure. Although specific terms may be employedherein, they are used in a generic and descriptive sense only and notfor purposes of limitation.

The invention claimed is:
 1. A method performed by an apparatus in afirst network that operates according to a first radio access technology(RAT), the method comprising: evaluating parameters and/or rules for aterminal device as part of an access network selection, traffic steeringand/or traffic aggregation procedure between the first network and asecond network, the second network operating according to a second RAT;starting a timer if the parameters and/or rules are satisfied; andadjusting operation of the timer in response to that a change orpotential change to the parameters and/or rules occurs prior to expiryof the timer, wherein in response to that the terminal device changescell prior to expiry of the timer, the adjusting of the operation of thetimer further comprises: allowing the timer to continue but preventingor aborting implementation of a result of the evaluation of the accessnetwork selection, traffic steering and/or traffic aggregation procedureupon expiry of the timer if updated parameters and/or rules have notbeen received.
 2. The method according to claim 1, wherein adjusting theoperation of the timer comprises one or more of: stopping the timer,suspending the timer, disabling the timer, restarting the timer, andresetting the timer.
 3. The method according to claim 1, whereinadjusting the operation of the timer comprises: adjusting the operationof the timer in response to that the parameters and/or rules are updatedprior to expiry of the timer.
 4. The method according to claim 3,wherein the updated parameters and/or rules differ from the evaluatedparameters and/or rules by more than a threshold.
 5. The methodaccording to claim 1, further comprising: receiving updated parametersand/or rules for a new cell; comparing the updated parameters and/orrules to the evaluated parameters and/or rules; implementing the resultof the evaluation of the access network selection, traffic steeringand/or traffic aggregation procedure upon expiry of the timer if theupdated parameters and/or rules are identical to the evaluatedparameters and/or rules; and discarding or aborting the result of theevaluation of the access network selection, traffic steering and/ortraffic aggregation procedure if the updated parameters and/or rules arenot identical to the evaluated parameters and/or rules.
 6. The methodaccording to claim 1, further comprising: receiving updated parametersand/or rules for a new cell; comparing the updated parameters and/orrules to the evaluated parameters and/or rules; implementing the resultof the evaluation of the access network selection, traffic steeringand/or traffic aggregation procedure upon expiry of the timer if theupdated parameters and/or rules are within a threshold of the evaluatedparameters and/or rules; and discarding or aborting the result of theevaluation of the access network selection, traffic steering and/ortraffic aggregation procedure if the updated parameters and/or rules arenot within the threshold of the evaluated parameters and/or rules. 7.The method according to claim 1, wherein adjusting the operation of thetimer comprises: performing one or more of stopping the timer,suspending the timer, disabling the timer, restarting the timer, andresetting the timer, according to an indication received from a node inthe first network.
 8. The method according to claim 1, wherein adjustingthe operation of the timer comprises: adjusting the operation of thetimer based on a state of the terminal device with respect to the secondnetwork.
 9. The method according to claim 1, wherein adjusting theoperation of the timer comprises: performing at least one of stoppingthe timer, suspending the timer, disabling the timer, restarting thetimer, and resetting the timer, only if the terminal device is notsteering traffic to the second network.
 10. The method according toclaim 1, further comprising: implementing a result of the evaluation ofthe access network selection, traffic steering and/or trafficaggregation procedure upon expiry of the timer.
 11. The method accordingto claim 1, further comprising: continuing to evaluate the parametersand/or rules once the timer is started; and stopping the timer inresponse to that the parameters and/or rules are no longer satisfied.12. The method according to claim 1, wherein the timer is aTsteering_(WLAN) timer.
 13. The method according to claim 1, wherein theapparatus is the terminal device.
 14. The method according to claim 1,wherein the apparatus is a network node in the first network.
 15. Anapparatus for use in a first network that operates according to a firstradio access technology (RAT), the apparatus comprising: at least onememory storing instructions; and at least one processor configured toexecute the instructions to: evaluate parameters and/or rules for aterminal device as part of an access network selection, traffic steeringand/or traffic aggregation procedure between the first network and asecond network, the second network operating according to a second RAT;start a timer if the parameters and/or rules are satisfied; and adjustoperation of the timer in response to that a change or potential changeto the parameters and/or rules occurs prior to expiry of the timer,wherein in response to that the terminal device changes cell prior toexpiry of the timer, the at least one processor is further configured toexecute the instructions to: allow the timer to continue but preventingor aborting implementation of a result of the evaluation of the accessnetwork selection, traffic steering and/or traffic aggregation procedureupon expiry of the timer if updated parameters and/or rules have notbeen received.
 16. The apparatus according to claim 15, wherein the atleast one processor is further configured to execute the instructions toadjust the operation of the timer by performing one or more of: stoppingthe timer, suspending the timer, disabling the timer, restarting thetimer, and resetting the timer.
 17. The apparatus according to claim 15,wherein the at least one processor is further configured to execute theinstructions to: receive updated parameters and/or rules for a new cell;compare the updated parameters and/or rules to the evaluated parametersand/or rules; implement the result of the evaluation of the accessnetwork selection, traffic steering and/or traffic aggregation procedureupon expiry of the timer if the updated parameters and/or rules areidentical to the evaluated parameters and/or rules; and discard or abortthe result of the evaluation of the access network selection, trafficsteering and/or traffic aggregation procedure if the updated parametersand/or rules are not identical to the evaluated parameters and/or rules.18. The apparatus according to claim 15, wherein the at least oneprocessor is further configured to execute the instructions to: receiveupdated parameters and/or rules for a new cell; compare the updatedparameters and/or rules to the evaluated parameters and/or rules;implement the result of the evaluation of the access network selection,traffic steering and/or traffic aggregation procedure upon expiry of thetimer if the updated parameters and/or rules are within a threshold ofthe evaluated parameters and/or rules; and discard or abort the resultof the evaluation of the access network selection, traffic steeringand/or traffic aggregation procedure if the updated parameters and/orrules are not within the threshold of the evaluated parameters and/orrules.
 19. The apparatus according to claim 15, wherein the at least oneprocessor is further configured to execute the instructions to: performat least one of stopping the timer, suspending the timer, disabling thetimer, restarting the timer, and resetting the timer, only if theterminal device is not steering traffic to the second network.
 20. Anon-transitory computer-readable medium storing a program codeexecutable by an apparatus in a first network that operates according toa first radio access technology (RAT), wherein the execution of theprogram code causes the apparatus to perform operations comprising:evaluating parameters and/or rules for a terminal device as part of anaccess network selection, traffic steering and/or traffic aggregationprocedure between the first network and a second network, the secondnetwork operating according to a second RAT; starting a timer if theparameters and/or rules are satisfied; and adjusting operation of thetimer in response to that a change or potential change to the parametersand/or rules occurs prior to expiry of the timer, wherein in response tothat the terminal device changes cell prior to expiry of the timer, theadjusting of the operation of the timer further comprises: allowing thetimer to continue but preventing or aborting implementation of a resultof the evaluation of the access network selection, traffic steeringand/or traffic aggregation procedure upon expiry of the timer if updatedparameters and/or rules have not been received.